Micro-Electro-Mechanical Systems (MEMS), which are suitable for integrated production, are micro devices or systems in which micro mechanisms, micro sensors, micro operators, and signal processing and control circuits are gathered as integral structures. MEMS are developed with the evolution of semiconductor integrated circuit precise manufacturing and super-precise mechanical manufacturing. Micro-electro devices applying MEMS technology are widely used in aviation, aerospace, environment supervision, biological medicine, and almost all fields human may access.
Compared with conventional mechanical structures, MEMS devices are smaller, at most not greater than one centimeter. Some MEMS devices only have several microns, and component layers thereof may have even less thickness. Since semiconductor materials, mainly silicon, are used in MEMS manufacturing, those proven techniques and processes applied in semiconductor integrated circuit manufacturing may be widely used to produce MEMS devices, thereby achieving volume production with relatively low costs. Micro mechanical components, applied as sensor, driving and moving structures, are essential to a MEMS device. Normally, a micro mechanical component, including a fixed support component and a movable free end which is suspended, needs to be disposed in a sealed cavity to avoid external influences.
Formations of sacrificial layers are required to enable a micro mechanical component to be suspended in a semiconductor structure, basic processing steps thereof including: forming a groove with a required size in a semiconductor dielectric layer; filling sacrificial material into the groove; forming a micro mechanical component on the sacrificial material; and removing the sacrificial material to suspend the micro mechanical component. To obtain more information of forming a MEMS device with a suspended micro mechanical component, please refer to US patent publication No. 2008290430A1 and 2007065967, and U.S. Pat. No. 7,239,712B1.
Current techniques have following drawbacks. Chemical vapor deposition (CVD) is usually used when filling a sacrificial material into the groove. To ensure the groove is completely filled, it is normally necessary that the sacrificial material may be deposited to cover the semiconductor dielectric layer out of the groove. Thereafter, the sacrificial material layer is thinned until the semiconductor dielectric layer is exposed using a chemical mechanical polishing (CMP) process. Therefore, the sacrificial material layer in the groove may be flush with the semiconductor dielectric layer around. Sacrificial materials commonly used in the art include amorphous carbon, some organic polymeric materials, and the like, which may be easily removed as gas using an ashing process. However, these materials are unlikely to react with polishing solutions due to special chemical characteristics thereof. As a result, the CMP process may have an unacceptable low polishing speed of the sacrificial material. Besides, the polishing speed of the sacrificial material is much faster than that of the semiconductor dielectric layer, which may, on the one hand, prolong the polishing period, on the other hand, bring a difficulty for stopping the polishing precisely on the surface of the semiconductor dielectric layer. A loss on the semiconductor dielectric layer's thickness is likely to occur.